I like the system in the book "timberframer's workshop"
Build "ponies" that are 16"-20" and use them to support long 8x material(giving a 24-28in working hieght).
If you haven't seen the book, the ponies are basically made from off cut 2x10's.
two peices make legs, these legs come together under the center of a third 12" long 2x10(like a pair of rafters with a plank balanced on top) then use some plywood off cuts to screw onto the sides of the 2x10's... these ponies are lighter than 8x blocks and, as Mr. Chappell says "make good stools"
one advantage of this system is that you can place timbers of any length(I use a pair of 20ft) on top of the ponies, making it possible to roll a dozen posts around on the same setup.
as far as height goes, it's hard to find a height that serves well for all tasks, I use the adze a lot and so I like a lower setup than average(24") I'd suggest trying different heights till you find the best.
